The present invention relates to a high pressure discharge lamp, such as a high pressure sodium light-emitting lamp, a metal halide lamp, and to a method of manufacturing such a high pressure discharge lamp. The present invention also relates to a composite electrode for a high pressure discharge lamp, and a method of manufacturing such a composite electrode.
Conventionally, such a high pressure discharge lamp comprises a vessel made of a non-conductive material (e.g. alumina) which forms an inner space filled with an ionizable light-emitting material and a starting gas, and which has opening portions at the ends thereof. The high pressure discharge lamp also comprises a composite electrode having a substantially cylindrical current conductor made of a conductive material (e.g. molybdenum) with a diameter which is substantially the same as that of the opening portion at one end of the vessel, and an electrode electrically connected to the current conductor. In this instance, a gap between the current conductor and the vessel is tightly sealed.
In this type of high pressure discharge lamp, there is a significant difference between the coefficient of thermal expansion of the conductive material forming the current conductor and that of the non-conductive material forming the vessel (for example, the coefficient of thermal expansion of alumina is 8xc3x9710xe2x88x926 Kxe2x88x921, and that of molybdenum is 6xc3x9710xe2x88x926 Kxe2x88x921). Owing to such a difference, when the high pressure discharge lamp is heated such as when the high pressure discharge lamp is in operation, there may be formed a gap between the current conductor on one hand and the vessel and/or the plug on the other hand. In this instance, as the molecular movement of the ionizable light-emitting material and the starting gas in the vessel becomes more active, these ionizable light-emitting material and starting gas may leak through the gap to outside of the vessel.
To avoid such a drawback, JP-A-2-132750 discloses a high pressure discharge lamp wherein, instead of forming the current conductor with only conductive material, the current conductor comprises a substantially cylindrical non-conductive material (e.g. alumina), which is same as that forming the vessel and coated by tungsten with a substantially uniform thickness over the surface of the non-conductive material. In this case, the composite electrode is composed such that a concave portion is provided at the bottom of the current conductor and an electrode is buried in the concave portion, or the electrode is connected to the current conductor with another member such as a cap. Also, the vessel and the composite electrode have been subjected to a co-firing into an integrated body, with the current conductor inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the composite electrode exposed to outside of the vessel. In this way, by composing most of the current conductor of a non-conductive material which is the same as the that forming the vessel, the adverse influence of the difference in the coefficient of thermal expansion between the conductive material (in this case, tungsten) and the non-conductive material is made substantially insignificant.
Also, JP-A-7-211292 discloses a high pressure discharge lamp wherein the current conductor comprises a substantially cylindrical non-conductive material, which is the same as that forming the vessel, and covered by a layer of mixture of platinum and alumina, a layer of platinum, and a layer of a mixture of platinum and alumina, with a substantially uniform thickness and one above the other over the surface of the non-conductive material. In this case, also, the composite electrode is composed such that a concave portion is provided at the bottom of this current conductor and an electrode is buried in the concave portion, or the electrode is connected to the current conductor with another member such as a cap. Therefore, the adverse influence of the difference in the coefficient of thermal expansion between the conductive material and the non-conductive material is made substantially insignificant.
Also, JP-A-8-273616 discloses a high pressure discharge lamp wherein the current conductor is formed with the substantially cylindrical non-conductive material, which is the same as that forming the vessel material, and covered by a halide-resistant metal such as niobium, tungsten, etc., with a substantially uniform thickness over the surface of the non-conductive material. In this case, the composite electrode is also composed such that a concave portion is provided at the bottom of this current conductor and an electrode is buried in the concave portion, or the electrode is connected to the current conductor with another member such as a cap. Therefore, the adverse influence of the difference in the coefficient of thermal expansion between the conductive material and the non-conductive material is made substantially insignificant.
However, in the high pressure discharge lamp disclosed in JP-A-2-132750, the composite electrode having the current conductor metallized with tungsten, whose melting point (3400xc2x0 C.) is higher than that of alumina (2015xc2x0 C.), is co-fired with the vessel into an integrated body. In this case, the melting point of tungsten in metallization is much different from that of alumina in metallization, so that the firing speed of tungsten is different from that of alumina. Also, the mutual wetting property of tungsten and aluminum is poor, and it is thus difficult to form a tightly metallized layer. Therefore, such a high pressure discharge lamp does not have a fully gas-tight property.
Further, in the high pressure discharge lamps disclosed in JP-A-7-211292 and JP-A-8-273616, the vessel and the composite electrode are not co-fired into an integrated body at least at one end of the vessel. Thus, a stronger junction cannot be formed between the non-conductive material of the vessel and metallized layer on the composite electrode, as compared to an arrangement wherein the vessel and the composite electrode are co-fired into an integrated body. Therefore, such a high pressure discharge lamp does not have a fully gas-tight property, either.
Moreover, in the composite electrodes for the high pressure discharge lamps disclosed in JP-A-2-132750, JP-A-7-21 1292 and JP-A-8-273616, it is preferred that the composite electrode can be easily manufactured and has a uniform thickness of the metallized layer over the surface of the current conductor.
On the other hand, in the conventional high pressure discharge lamp, when the gap between the current conductor and the vessel is tightly sealed, there is used a frit seal. In this case, the proximity of the opening portion at one end of the vessel is heated to a predetermined temperature (e.g. 1500xc2x0 C.). On such occasion, the other end of the vessel is cooled in order to prevent the molecular movement of the ionizable light-emitting material and starting gas from being active such that they are prevented from leakage through the frit seal of the vessel to outside of the vessel. However, in spite of such cooling, the inner part of the vessel is still heated to a substantial temperature (e.g. 300-400xc2x0 C.) even for a limited period (e.g. 1-3 minutes). Thus, there still remains the possibility for the ionizable light-emitting material and starting gas to more or less leak through the frit seal of the vessel to outside of the vessel.
Moreover, in manufacturing the composite electrode by jointing the electrode to the current conductor, it is preferable to have a high bonding strength between the electrode and the current conductor, a high corrosion resistance, and a, high conductivity.
It is a first object of the present invention to provide a high pressure discharge lamp having a satisfactory gas-tight property while fully maintaining the required conductivity, as well as a method of manufacturing the same.
It is a second object of the present invention to provide the high pressure discharge lamp capable of preventing the ionizable light-emitting material and starting gas filled in the inner portion of the vessel from leaking to outside of the vessel at the time of tightly sealing, as well as a method of the manufacturing the same.
It is a third object of the present invention to provide the composite electrode for a high pressure discharge lamp, which is easy to manufacture and realize a uniform thickness of the metallized layer over the surface of the current conductor, as well as a method of the manufacturing the same.
It is a fourth object of the present invention to provide the high pressure discharge lamp having a high bonding strength between the electrode and the current conductor, a high corrosion resistance, and a high conductivity.
The high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a substantially cylindrical current conductor with a diameter which is substantially the same as a diameter of the opening portion at one end of the vessel, and an electrode electrically connected to the current conductor;
said current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof;
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said composite electrode having been subjected to a co-firing into an integrated body, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the composite electrode is exposed to outside of the vessel.
According to the invention, the current conductor is formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the composite electrode comprising such a current conductor and the vessel have been subjected to a co-firing into an integrated body. By having been subjected to a co-firing into an integrated body in such a manner, the non-conductive material in the vessel and the substantially cylindrical member is diffused into the layer of the mixture formed on a surface of the substantially cylindrical member so that a strong joining structure is formed between the vessel and the substantially cylindrical member.
Here, in order to form such a strong joining structure, it is necessary for the metal of the mixture coated on at least a tubular surface thereof the substantially cylindrical member to contain a metal which has melting point comparatively close to those of the nearly cylindrical member and. the vessel, etc, and has enough halide resistance, and for its non-conductive material to contain a material which is the same as that forming the vessel and the substantially cylindrical member. To fulfill such requirements, according to the high pressure discharge lamp of the invention, the metal of the mixture coated on at least a tubular surface of the substantially cylindrical member contains not less than 50 vol. % of molybdenum which has halide resistance and lower melting point (2623xc2x0 C.) than that of tungsten, and the non-conductive conductive material of the mixture coated on the substantially cylindrical member contains not less than 50 vol. % of a material which is the same as that forming the vessel.
Therefore, with the current conductor being formed by the substantially cylindrical member coated with the mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the vessel and the composite electrode having been subjected to a co-firing into an integrated body to form a strong joining structure between the vessel and the substantially cylindrical member, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity. Further, a substantially cylindrical member is understood to mean not only a cylindrical member itself but also a member in which a concave portion is provided at the bottom of the cylindrical member and a member in which the bottom of the cylindrical member is inclined to an axis thereof as described hereinafter.
Preferably, the content of said metal of the mixture coated on said substantially cylindrical member is 30 to 70 vol. %.
As the content of the metal of the mixture coated on at least a tubular surface of the substantially cylindrical member becomes high, the conductivity of the high pressure discharge lamp improves. On the other band, as the content of the non-conductive material of the mixture becomes high, the gas tight property of the high pressure discharge lamp improves. As the result of various experiments by the inventor, in order to maintain the gas tight property while maintaining full conductivity, it is found that the preferable content of the metal of the mixture is 30 to 70 vol. %.
More preferably, said metal of the mixture coated on said substantially cylindrical member is made of molybdenum, said non-conductive material of the mixture is made of a material which is same as that forming said vessel.
In order that the vessel and the composite electrode have subjected to a co-firing into an integrated body to form a strong joining structure between the vessel and the nearly cylindrical shaped member of the current conductor, it is preferable that the content of molybdenum in the metal of the mixture coated on at least a tubular surface of the substantially cylindrical member is as high as possible, and the content of the material which is the same as that forming the vessel in the non-conductive material of the mixture is as high as possible. Therefore, it is the most suitable for the mixture to compose of molybdenum and the material which is the same as that forming the vessel.
Further, molybdenum is understood to mean not only pure molybdenum but also that containing a few impurities, and the material which is the same as that forming the vessel is understood to mean not only completely the same as that forming the vessel but also that containing few impurities.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a substantially cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at one end of the vessel, and an electrode electrically connected to the current conductor;
said current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material; said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel on at least a tubular surface thereof;
said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, said gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, the substantially cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at one end of the vessel is formed by the substantially cylindrical member coated with mixture of the metal and the non-conductive material on at least a tubular surface thereof and the current conductor and the vessel are so arranged relative to each other as to leave a gap therebetween, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, the gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel. By tight sealing with such a layer in such a manner, only proximity of the opening portion of one end of the vessel is heated in a moment. Unlike the prior high pressure discharge lamp in which tight sealing is effected with a frit seal, it is not heated over a certain temperature (eg. 300-400xc2x0 C.) for a certain time (e.g. 1-3 minutes) so that the movement of the ionizable light-emitting material and the starting as does not become active and leak the ionizable light-emitting material and the starting gas to outside of the vessel.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; a first composite electrode having a substantially cylindrical current conductor with a diameter which is substantially the same as a diameter of the opening portion at one end of the vessel, and an electrode electrically connected to the current conductor; and a second composite electrode having a substantially cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at the other end of the vessel, and an electrode electrically connected to the current conductor;
each of said current conductors of the first and second composite electrodes being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof,
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said first composite electrode having been subjected to a co-firing into an integrated body, with the first composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the first composite electrode is exposed to outside of the vessel; and said current conductor of the second composite electrode and said vessel being so arranged relative to each other as to leave a gap therebetween, with the second composite electrode inserted into the opening portion at the other end of the vessel so that the electrode is exposed to the inner space with one end of the second composite electrode is exposed to outside of the vessel, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-filing into an integrated body, the high pressure discharge lamp according to the invention have a fully gas tight property while maintaining full conductivity.
In this case, although the gap may be tight sealed with such a layer, it may be tight sealed with the frit seal as usual.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a cylindrical current conductor with a diameter which is substantially same as a diameter of the opening portion at one end of the vessel, and an electrode jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel;
said current conductor of the composite electrode being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material at on at least a tubular surface;
said metal of the mixture coated on said cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said composite electrode having been subjected to a co-firing into an integrated body, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, as the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Also, by jointing the electrode by welding or metallizing at a side of current conductor, a bonding area between the current conductor and the electrode or an area contacting the mixture to the current conductor and the electrode increases, so that the bonding strength between the current conductor and the electrode can further improve.
Preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can improve much more. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conducting material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at one end of the vessel, and an electrode jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel;
said current conductor of the composite electrode being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof;
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, said gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, as only the proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting material and the starting gas may not leak to outside of the vessel.
Also, as the electrode is jointed by welding or metallizing at a bottom or a made of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, and the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a nor-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; a first composite electrode having a cylindrical current conductor with a diameter which is substantially the same as a diameter of the opening portion at one end of the vessel, and an electrode jointed by welding or metallizing at a bottom of the current conductor exposed to inside of the vessel; and a second composite electrode having a cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at the other end of the vessel, and an electrode jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel;
each of said current conductors of the first and second composite electrodes being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof;
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said first composite electrode having been subjected to a co-firing into an integrated body, with the first composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the first composite electrode is exposed to outside of the vessel; and said current conductor of the second composite electrode and said vessel being so arranged relative to each other as to leave a gap therebetween, with the second composite electrode inserted into the opening portion at the other end of the vessel so that the electrode is exposed to the inner space with one end of the second composite electrode is exposed to outside of the vessel, said gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, instead of gas tight sealing the gap between the current conductor and the vessel at the other end of the vessel by the layer of the mixture of the metal and the non-conductive material gas tight sealing may be effected with a frit seal such as used in usual.
Also, as the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, and the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a substantially cylindrical current conductor with a diameter which is substantially same as a diameter of the opening portion at one end of the vessel and a bottom inclined to an axis thereof exposed to inside of the vessel, and an electrode jointed by welding or metallizing at the bottom exposed to inside of the vessel;
said current conductor of the composite electrodes being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof;
said metal of the mixture coaled on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said composite electrode having been subjected to a co-firing into an integrated body, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the composite electrode is exposed to outside of the vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least one side, and the composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property and full conductivity.
In this case, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material which has a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material which joints the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portion at both ends thereof; a composite electrode having a substantially cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at one end of the vessel and a bottom inclined to an axis thereof exposed to inside of the vessel, and an electrode jointed by welding or metallizing at the inclined bottom of the current conductor exposed to inside of the vessel;
said current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof;
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the composite electrode is exposed to outside of the vessel, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, as only proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting material and the starting gas may not leak to outside of the vessel.
Also, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conducting material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portion at both ends thereof; a first composite electrode having a substantially cylindrical current conductor with a diameter which is substantially the same as a diameter of the opening portion at one end of the vessel and a bottom inclined to an axis thereof exposed to inside of the vessel, and an electrode jointed by welding or metallizing at the bottom of the current conductor exposed to inside of the vessel; and a second composite electrode having a substantially cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at the other end of the vessel and a bottom inclined to an axis thereof exposed to inside of the vessel, and an electrode jointed by welding or metallizing at the bottom of the current conductor exposed to inside of the vessel;
each of said current conductors of the first and second composite electrodes being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof;
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said first composite electrode having been subjected to a co-firing into an integrated body, with the first composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the first composite electrode is exposed to outside of the vessel; and said current conductor of the second composite electrode and said vessel being so arranged relative to each other as to leave a gap therebetween, with the second composite electrode inserted into the opening portion at the other end of the vessel so that the electrode is exposed to the inner space with one end of the second composite electrode is exposed to outside of the vessel, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is same as that forming said vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, instead of tight sealing the gap between the current conductor and the vessel at the other end of the vessel by the layer of the mixture of the metal and the non-conductive metal, gas tight sealing may be effected with a frit seal such as used in usual.
Also, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor exposed to inside of the vessel is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conducting material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider tan the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a cylindrical current conductor with a diameter which is substantially the same as a diameter of the opening portion at one end of the vessel, and an electrode jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel;
said current conductor of the composite electrode being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, an axis of the electrode substantially corresponding to that of an electrode to be opposite to the electrode,
said metal of the mixture coated on said cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said composite electrode having been subjected to a co-firing into an integrated body, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the composite electrode is exposed to outside of the vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case as the electrode is jointed by welding or metallizing at a side of the current conductor, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Further, to promote ignition of the high pressure discharge lamp, it is preferable for an axis of the electrode to substantially correspond to that of an electrode to be opposite to the electrode. According to the invention, as an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; and a composite electrode having a cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at one end of the vessel, and an electrode jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel;
said current conductor of the composite electrode being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, an axis of the electrode substantially corresponding to that of an electrode to be opposite to the electrode,
said metal of the mixture coated on said cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, with the composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, as only the proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting and the starting gas may not leak to outside of the vessel.
Also, as an axis of the electrode substantially corresponds to an axis of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof; a first composite electrode having substantially cylindrical current conductor with a diameter which is substantially same as a diameter of the opening portion at one end of the vessel, and an electrode jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel; and a second composite electrode having a substantially cylindrical current conductor with a diameter which is smaller than a diameter of the opening portion at the other end of the vessel, and an electrode jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel;
each of said first and second current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, an axis of the electrode of the first composite electrode substantially corresponding to that of the second composite electrode;
said metal of the mixture coated on said substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said first composite electrode having been subjected to a co-firing into an integrated body, with the first composite electrode inserted into the opening portion at one end of the vessel so that the electrode is exposed to the inner space with one end of the first composite electrode is exposed to outside of the vessel; and said current conductor of the second composite electrode and said vessel being so arranged relative to each other as to leave a gap therebetween, with the second composite electrode inserted into the opening portion at the other end of the vessel so that the electrode is exposed to the inner space and one end of the second composite electrode is exposed to outside of the vessel, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, instead of gas light sealing the gap between the current conductor and the vessel at the other end of the vessel by the layer of the mixture of the metal and the non-conductive material, gas tight sealing may be effected with a frit seal such as used in usual.
Also, as an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing as a side of the current conductor.eposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof and a metal or a mixture of a metal and a non-conductive material coated at the proximity of at least one opening portion; an electrode jointed by metallizing at the proximity of the opening portion so as to expose to the inner space; and a plug made of a non-conductive material with a diameter which is substantially same as a diameter of the at least one opening portion;
said metal of the mixture coated on the opening portion containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said vessel and said plug having been subjected to a co-firing into an integrated body, with the plug inserted into the at least one opening portion.
By jointing the electrode at the proximity of the opening portion, an area contacting the mixture to the electrode and the proximity of the opening portion is enough, so that bonding strength to the electrode becomes high.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another high pressure discharge lamp according to the invention comprises a vessel made of a non-conductive material which forms an inner space filled with an ionizable light-emitting material and a starting gas, and has opening portions at both ends thereof and a metal or a mixture of a metal and a non-conductive material coated at the proximity of at least one opening portion; an electrode jointed by metallizing at the proximity of the opening portion so as to expose to the inner space; and a plug made of a non-conductive material with a diameter which is smaller than a diameter of the at least one opening portion;
said metal of the mixture coated on the opening portion containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
said plug and said vessel being so arranged relative to each other as to leave a gap therebetween, with the plug inserted into the opening portion coated on the mixture, said gap being tightly sealed with metallic layer or a layer made of a mixture of a metal and material which is the same as that forming said vessel.
By jointing the electrode at the proximity of the opening portion, an area contacting the mixture to the electrode and the proximity of the opening portion is enough, so that bonding strength to the electrode becomes high.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
The composite electrode for a high pressure discharge lamp according to the invention has a current conductor which forms a cylindrical members made of non-conductive material coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof; and an electrode jointed by welding or metallizing at a bottom or a side of the current conductor,
said metal of the mixture coated on said cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel.
As the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents from a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another composite electrode for a high pressure discharge lamp according to the invention has a current conductor which forms a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and has a bottom inclined to an axis thereof; and an electrode jointed by welding or metallizing at the inclined bottom;
said metal of the mixture coated on said cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel.
As the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents from a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another composite electrode for a high pressure discharge lamp according to the invention has a current conductor which forms a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof; and an electrode jointed by welding or metallizing at a side of the current conductor; an axis of the electrode substantially corresponding to that of an electrode to be opposite to the electrode,
said metal of the mixture coated on said cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel.
As an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
The method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of; forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode electrically connected to the current conductor;
said metal of the mixture coating on the substantial cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel and said substantially cylindrical current conductor has substantially same diameter as a diameter of the opening portion at one end of the vessel;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and co-firing said vessel and said composite electrode into an integrated body.
According to the method of manufacturing a high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention have a full gas tight property while maintaining full conductivity.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode electrically connected to the current conductor;
said metal of the mixture coating on the substantial cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, and said substantially cylindrical current conductor has smaller diameter than a diameter of the opening portion at one end of the vessel;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another method of manufacturing a high pressure discharge lamp of the invention, as only the proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting material and the starting gas may not leak to outside of the vessel.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming first and second composite electrodes which have a current conductor formed by a substantially cylindrical member coated with a mixture of a metal on at least a tubular surface thereof and a non-conductive material and an electrode electrically connected to the current conductor, respectively;
said metal of the mixture coating on the substantial cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, said substantially cylindrical current conductor of the first composite electrode has substantially same diameter as a diameter of the opening portion at one end of the vessel and said substantially cylindrical current conductor of the second composite electrode has smaller diameter than a diameter of the opening portion at the other end of the vessel;
inserting said first composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the first composite electrode is exposed to outside of the vessel, and co-firing said vessel and said first composite electrode into an integrated body; and inserting said second composite electrode into the opening portion at the other end of the vessel such that the electrode is exposed to the inner space and one end of the second composite electrode is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is same as that forming said vessel.
According to another method of manufacturing a high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while and full conductivity.
In this case, the gap may be gas tight sealed with a frit seal as usual.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode jointed by welded or metallizing at a bottom or a side of the current conductor;
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, and said cylindrical current conductor has substantially same diameter as a diameter of the opening portion at one end of the vessel;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and co-firing said vessel and said composite electrode into an integrated body.
According to another method of manufacturing a high pressure discharge lamp of the invention, with the current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, as the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conducting material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode jointed by welded or metallizing at a bottom or a side of the current conductor;
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, and said cylindrical current conductor has smaller diameter than a diameter of the opening portion at one end of the vessel;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of be vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another method of manufacturing a high pressure discharge lamp of the invention, as only the proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting material and the starting gas may not leak to outside of the vessel.
Also, as the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming first and second composite electrodes which have a current conductor formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode jointed by welded or metallizing at a bottom or a side of the current conductor, respectively;
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, said current conductor of the first composite electrode has substantially the same diameter as a diameter of the opening portion at one end of the vessel, and said current conductor of the second composite electrode has smaller diameter than a diameter of the opening portion at the other end of the vessel;
inserting said first composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the first composite electrode is exposed to outside of the vessel, and co-firing said vessel and said first composite electrode into an integral body; and inserting said second composite electrode into the opening portion at the other end of the vessel such that the electrode is exposed to the inner space and one end of the second composite electrode is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, instead of tight sealing the gap between the current conductor and the vessel at the other end of the vessel by the layer of the mixture of the metal and the non-conductive material, gas tight sealing may be effected with a frit seal such as used in usual.
Also, as the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and having at least one bottom inclined to an axis thereof, and an electrode jointed by welding or metallizing at the inclined bottom;
said metal of the mixture coating on the substantially cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, and said current conductor has substantially the same diameter as a diameter of the opening portion at one end of the vessel;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and co-firing said vessel and said composite electrode into an integral body.
According to another method of manufacturing a high pressure discharge lamp of the invention, with the current conductor of the composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the composite electrode and the vessel having been subjected to co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
Further, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further increase. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and having at least one bottom inclined to an axis thereof, and an electrode jointed by welding or metallizing at the inclined bottom;
said metal of the mixture coating on the substantially cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, and said current conductor has smaller diameter than a diameter of the opening portion at one end of the vessel;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another method of manufacturing a high pressure discharge lamp of the invention, as only proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting and the starting gas may not leak to outside of the vessel.
Further, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming first and second composite electrodes which have a current conductor formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and having at least one bottom inclined to an axis thereof, and an electrode jointed by welding or metallizing at the inclined bottom, respectively;
said metal of the mixture coating on the substantially cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel said current conductor of the first composite electrode has substantially the same diameter as a diameter of the opening portion at one end of the vessel, and said current conductor of the second composite electrode has smaller diameter than a diameter of the opening portion at the other end of the vessel;
inserting said first composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the first composite electrode is exposed to outside of the vessel, and co-firing said vessel and said composite electrode into an integral body; and inserting said second composite electrode into the opening portion at the other end of the vessel such that the electrode is exposed to the inner space and one end of the second composite electrode is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming the vessel.
According to another method of manufacturing a high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integrated body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, the gap may be sealed with a frit seal such as used in usual.
Also, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode jointed by welding or metallizing at a side of the current conductor;
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, said cylindrical current conductor has substantially same diameter as a diameter of the opening portion at one end of the vessel, and an axis of the electrode substantially corresponding to that of an electrode to be opposite to the electrode;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and co-firing said vessel and said composite electrode into an integral body.
According to another method of manufacturing a high pressure discharge lamp of the invention, with the current conductor of the composite electrode being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the composite electrode and the vessel having been subjected to a co-firing into an integral body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
Further, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Moreover, as an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non conductive material formed with an inner space filled with an ionizable light-emitting material and a sting gas, and with opening portions at the ends of the inner space; and forming a composite electrode which has a current conductor formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode jointed by welding or metallizing at a side of the current conductor;
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, said cylindrical current conductor has smaller diameter than a diameter of the opening portion at one end of the vessel, and an axis of the electrode substantially corresponding to that of an electrode to be opposite to the electrode;
inserting said composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the composite electrode is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another method of manufacturing a high pressure discharge lamp of the invention, as only proximity of the opening portion of one end of the vessel is heated in a moment, the ionizable light-emitting and the starting gas may not leak to outside of the vessel.
Further, As the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider than the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Moreover, as an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, and with opening portions at the end of the inner space; and forming first and second composite electrodes which have a current conductor formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof and an electrode jointed by welding or metallizing at a side of the current conductor, respectively;
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel, said cylindrical current conductor of the first composite electrode has substantially same diameter as a diameter of the opening portion at one end of the vessel, said current conductor of the second composite electrode has smaller diameter than a diameter of the opening portion at the other end of the vessel, and an axis of the electrode of the first composite electrode substantially corresponding to that of the second composite electrode;
inserting said first composite electrode into the opening portion at one end of the vessel such that the electrode is exposed to the inner space and one end of the first composite electrode is exposed to outside of the vessel, and co-firing said vessel and said composite electrode into an integral body; and inserting said second composite electrode into the opening portion at the other end of the vessel such that the electrode is exposed to the inner space and one end of the second composite is exposed to outside of the vessel, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being gas tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
According to another high pressure discharge lamp of the invention, with the current conductor of the first composite electrode being formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and the first composite electrode and the vessel having been subjected to a co-firing into an integral body, the high pressure discharge lamp according to the invention has a fully gas tight property while maintaining full conductivity.
In this case, the gap may be sealed with a frit seal such as commonly used.
Further, as the electrode is jointed by welding or metallizing at the inclined bottom, an area contacting the mixture to the current conductor is wider th the case where the electrode is jointed at a bottom of the current conductor whose bottom is perpendicular to an axis thereof, so that the bonding strength between the electrode and the current conductor improves.
Moreover, as an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conducting material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, with opening portions at the ends of the inner space and a mixture of a metal and a non-conductive material coating on the proximity of at least one opening portion; forming an electrode; and forming a plug having a substantially same diameter as a diameter of the at least one opening portion;
said metal of the mixture coating on the proximity of the opening portion containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
jointing said electrode by metallizing at the proximity of the opening portion, inserting said plug into the at least one opening portion such that the electrode is exposed to the inner space, and co-firing said vessel and said plug into an integral body.
By jointing the electrode at the proximity of the opening portion, an area contacting the mixture to the electrode and the proximity of the opening portion is enough, so that bonding strength to the electrode becomes high.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the nonconductive material which joints the electrode and the current conductor, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a high pressure discharge lamp according to the invention comprises the steps of: forming a vessel made of a non-conductive material formed with an inner space filled with an ionizable light-emitting material and a starting gas, with opening portions at the ends of the inner space and a mixture of a metal and a non-conductive material coating on the proximity of at least one opening portion; forming an electrode; and forming a plug having a smaller diameter than a diameter of the at least one opening portion;
said metal of the mixture coating on the proximity of the opening portion containing not less than 50 vol. % of molybdenum, said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel;
jointing said electrode by metallizing at the proximity of the opening portion, inserting said plug into the at least one opening portion such that the electrode is exposed to the inner space, and said current conductor and said vessel being so arranged relative to each other as to leave a gap therebetween, said gap being tightly sealed with a metallic layer or a layer made of a mixture of a metal and a material which is the same as that forming said vessel.
By jointing the electrode at the proximity of the opening portion, an area contacting the mixture to the electrode and the proximity of the opening portion is enough, so that bonding strength to the electrode becomes high.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
The method of manufacturing a composite electrode for a high pressure discharge lamp according to the invention comprises the steps of: forming a current conductor made of a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, and an electrode welded or metallized jointed at a bottom or a side of the current conductor,
said metal of the mixture coating on the cylindrical member containing not less than 50 vol. % of molybdenum, and said non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel.
In this case, as the electrode is jointed by welding or metallizing at a bottom or a side of the current conductor which is formed by a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, it is possible to coat the mixture of the metal and the non-conductive material over a surface of the current conductor with more uniform thickness than the case where the electrode is buried on the concave portion at the bottom of this current conductor, and it is possible to compose the composite electrode simpler than the case where another member such as a cap is provided.
Preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metallizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a composite electrode for a high pressure discharge lamp according to the invention comprises the steps of: forming a current conductor made of a substantially cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof, with a bottom inclined to an axis thereof; and jointing an electrode by welding or metallizing at the inclined bottom;
said metal of the mixture coating on the substantially cylindrical member containing not less than 50 vol. % of molybdenum, and non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel.
As the electrode is jointed by welding or metallizing at the inclined bottom, a bonding strength between the cement conductor and the electrode is higher than the case the electrode is jointed at a bottom perpendicular to an axis thereof.
Preferably, at least one end o the current conductor is rounded, the electrode is jointed by metallizing at the rounded end.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case there the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Moreover, such a rounded end prevents a stress concentration at the proximity of the end.
More preferably, the electrode is jointed by welding or metallizing at a side of the current conductor, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
More preferably, at least one end of the current conductor is rounded, the electrode is jointed by metalizing at the rounded end, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By providing such a rounded end, an area contacting the mixture to the current conductor is wider than the case where the rounded end is not provided, so that the bonding strength between the current conductor and the electrode can further improve. Also, as an area which contacts the mixture using the joint of the current conductor and the electrode to the mixture coated on the cylindrical member increases, the conductivity of the composite electrode becomes higher. Further, such a rounded end prevents a stress concentration at the proximity of the end. Moreover, by using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Another method of manufacturing a composite electrode for high pressure discharge lamp according to the invention comprises the steps of: forming a current conductor made of a cylindrical member coated with a mixture of a metal and a non-conductive material on at least a tubular surface thereof; and jointing an electrode by welding or metallizing at a side of the current conductor so that an axis of the electrode substantially matches with that of an electrode to be opposite to the electrode;
said metal of the mixture coating on the substantially cylindrical member containing not less than 50 vol. % of molybdenum, and non-conductive material of the mixture containing not less than 50 vol. % of a material which is the same as that forming said vessel.
Also, as an axis of the electrode substantially corresponds to that of an electrode to be opposite to the electrode, it is possible to promote ignition of the high a pressure discharge lamp.
Preferably, the electrode is jointed by welding or metallizing at a side of the current conductor exposed to inside of the vessel, a metal or a mixture of a metal and a non-conductive material having a higher melting point and/or a higher corrosion resistance than a metal or a mixture of a metal and a non-conductive material jointing the electrode and the current conductor is coated on the joint portion of the electrode and the current conductor and the proximity thereof.
By using the metal or the mixture of the metal and the non-conductive material which has a higher melting point and/or a higher corrosion resistance than the metal or the mixture of the metal and the non-conductive material which joints the electrode and the current conductor in such a way, the bonding strength between the current conductor and the electrode and/or the corrosion resistance further improves.
Further, when manufacturing the electrode or firing an arc tube, an external lead, etc (Mo, Ni, etc) is attached to the side of metallized coating of the composite electrode and the vessel and the composite electrode are co-fired into an integrated body.